ided for regulating the position of the dredger in regard to its
work.

_Barge-loading Dredgers_ used formerly to be provided with two ladders,
one on each side of the vessel, or contained in wells formed in the
vessel near each side. Two ladders were adopted, partly to permit the
dredger to excavate the material close to a quay or wall, and partly to
enable one ladder to work while the other was being repaired. Bucket
ladder dredgers are now, however, generally constructed with one central
ladder working in a well; frequently the bucket ladder projects at
either the head or stern of the vessel, to enable it to cut its own way
through a shoal or bank, a construction which has been found very
useful. In one modification of this method the bucket ladder is
supported upon a traversing frame which slides along the fixed framing
of the dredger and moves the bucket ladder forward as soon as it has
been sufficiently lowered to clear the end of the well. In places where
a large quantity of dredging has to be done, a stationary dredger with
three or four large hopper barges proves generally to be the most
economical kind of plant. It has, however, the disadvantage of requiring
large capital expenditure, while the dredger and its attendant barges
take up an amount of space which is sometimes inconvenient where traffic
is large and the navigable width narrow. The principal improvements made
in barge-loading dredgers have been the increase in the size of the
buckets and the strength of the dredging gear, the application of more
economical engines for working the machinery, and the use of frictional
gearing for driving the ladder-hoisting gear. It is very important that
the main drive be fitted with the friction blocks or clutches before
alluded to.

Up to the year 1877 dredgers were seldom made with buckets of a
capacity exceeding 9 cub. ft., but since that time they have been
gradually increased in capacity. In the dredger "Melbourne,"
constructed by Messrs William Simons & Co. to the design and
specification of Messrs Coode, Son & Matthews, about the year 1886,
the buckets had a capacity of 22 cub. ft., the dredger being capable
of making 37 ft. of water. The driving power consists of two pairs of
surface-condensing engines, each of 250 i.h.p., having cylinders 20
in. and 40 in. in diameter respectively, with a 30 in. stroke, the
boiler pressure being 90 lb. per sq. in. The vessel is 200 ft. long
by 36 ft.